湖南第2代杉木幼林的水文学过程及养分动态研究

采用小集水区技术和定位研究方法 ,根据连续 3a观测所取得的数据 ,对湖南会同第 2代杉木幼林的水量平衡和养分元素的地球化学循环进行了研究。结果表明 :该森林生态系统年降雨输入为 1170 6mm ,其中 3 5 3mm以树干茎流形式进入林地 ,占降雨量的 0 3% ,林内穿透水为 10 17 3mm ,占 86 9% ,另外林冠年截留量为 149 77mm ,占年降雨量的 12 8%。以径流形式流出该系统的水量为 42 8 0 5mm ,占年降雨量的 36 5 7% ,其中地表径流和地下径流分别占总径流的 4 31%和 95 6 9%。系统另一输出形式蒸散量为 86 2 6 4mm ,为年降雨量的 6 2 2 %。在该森林生态系统中 ,由降雨输入的N、P、K、Ca、Mg等元素的总量为 5 3 173kg·hm- 2 ·a- 1 ,径流输出量为 42 5 6 3kg·hm- 2 ·a- 1 ,净积累量为 10 6 10kg·hm- 2 ·a- 1 。与稳定态的第 1代杉木林相比 ,第 2代杉木幼林的林冠截留量成倍减少 ,地表径流、地下径流量和径流总量都高于第 1代杉木林 ,其涵养水源的能力相对较弱 ,抵抗外界干扰的能力比稳定态的第 1代杉木林差。从生物循环来看 ,第 2代杉木幼林的养分存留量大 ,表明第 2代杉木幼林将从土壤中吸收的养分大量地保存在林木中 ,造成土壤中养分的逐渐减少 ,维持持久的林地生产力应引起重视。第 2代杉木幼林

HYDROLOGIC PROCESS AND NUTRIENT DYNAMICS OF YOUNG SECOND-ROTATION CHINESE FIR PLANTATION

Based on the small watershed technique and the located observation method,the data collected in 3 consecutive years were used for analyzing the water balance and nutrients geochemical cycling in the second\|rotation Chinese fir plantation.The results showed that the average annual rainfall of the ecosystem was 1170.6mm,86.9%，0.3% and 12.8% of which were allocated to throughfall,stemflow and canopy interception,respectively.The annual runoff was 428.05mm,that was 36.57% of the annual rainfall.The surface runoff and ground runoff accounted for 4.31% and 95.69% of the total runoff.The estimated evapotranspiration of the second\|rotation Chinese fir plantation was 862.64mm,that was 62.2% of the annual rainfall.In the process of biological cycling,the annual uptake of 5 nutrient elements (N,P,K,Ca and Mg) in the second\|rotation Chinese fir plantation was up to 140.658kg*hm-2*a-1,annual return and retention was 73.988kg*hm-2*a-1 and 66.67kg*hm-2*a-1,respectively.The cycling rate accounted for 0.53.The total nutrient input of N,P,K,Ca and Mg reached 53.173kg*hm-2*a-1,and output was 42.563kg*hm-2*a-1.The net nutrient accumulation was 10.610kg*hm-2*a-1. 　　In contrast to the first\|rotation Chinese fir plantation,the hydrologic process and nutrient dynamics of the second\|rotation had different characteristics.The canopy interception rate in the second\|ration was lower than that in the first rotation.In the second\|rotation Chinese fir plantation,the monthly runoff varied with the pace of the rainfall,and the annual retention was higher while net nutrient accumulation was lower.These statistics revealed that the second\|rotation Chinese fir had lower capacity of water regulation and disturbance resistance.The trees consumed more nutrients and the ecosystem was in the biological restoration stage.